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IMSL_ELK

Syntax | Return Value | Arguments | Keywords | Discussion | Example | Version History

The IMSL_ELK function evaluates the complete elliptic integral of the kind K(x).


Note
This routine requires an IDL Analyst license. For more information, contact your ITT Visual Information Solutions sales or technical support representative.

Syntax

Result = IMSL_ELK(x [, /DOUBLE])

Return Value

The complete elliptic integral K(x).

Arguments

x

Argument for which the function value is desired.

Keywords

DOUBLE

If present and nonzero, double precision is used.

Discussion

The complete elliptic integral of the first kind is defined to be:

The argument x must satisfy 0 £ x < 1; otherwise, IMSL_ELK returns the largest representable floating-point number.

The function K(x) is computed using IMSL_ELRF and the relation
K(x) = RF(0, 1 - x, 1).

Example

The integral K(0) is evaluated. 

PRINT, IMSL_ELK(0.0)  
      1.57080

Version History

6.4
Introduced

  IDL Online Help (March 06, 2007)